(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

if H and K are arbitrary subgroup of G, prove that HK=KH iff HK is a subgroup of G

2. Relevant equations

n/a

3. The attempt at a solution

no problem to prove => direction

for <= i can prove KH is a subset of HK

only i got troubled to show HK ia subset of KH

x in HK

x=hk for some h in H ,k in K

i manipulate it many ways and always got the form x=khk for some h in H ,k in K

HELP, and sorry no latex ,i'm very buzy now ;P

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# Homework Help: Help with Subgroups

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